Spunbonded olefin sheet material is very desirable packaging material for numerous uses, including envelopes, (flat or expansion) pouches, folders, sleeves, etc. Spunbonded olefin sheet material is relatively light for its strength in comparison to paper and other, conventional packaging materials. One reason it is good for packaging is its strength. Typically, paper weighing two to three times as much as spunbonded olefin sheet is required to provide comparable strength.
Spunbonded olefin sheet has other characteristics making it desirable for packaging. The dense fiber network forming the sheet material offers extremely high resistance to tear, puncture and abrasion. Spunbonded olefin sheet material has excellent resistance to waterborne soil and good resistance to degradation from age unless overly exposed to ultraviolet light. It is inert to most acids, unaffected by water or highly polar solvents and is therefore readily washable. It further meets the requirements of the Federal Flame Fabrics Act. Spunbonded olefin sheet is sold in different forms which have different characteristics in terms of tear strengths, tensile strengths, smoothness, porosity, flexibility and softness.
Either cold applied adhesives such as polyvinyl acetate resin (PVA) or hot-melt pressure sensitive adhesive (PSA) are typically used with spunbonded olefin material in packaging. Such adhesives are very tenacious and stick firmly to the generally smooth and non-porous olefin sheet. Hot-melt adhesive can be applied during package fabrication to the closure flap as a pressure-sensitive adhesive closure with a release material liner protecting the closure until it is time to seal the mouth of the package.
Because hot-melt adhesives are so tenacious, considerable force is necessary to separate the flap from the body of the package on which such adhesives are used. Typically, the opening of an olefin sheet package closed with hot-melt adhesive results in a partial tearing away of filaments from the remaining surface of the olefin sheet and an extension from the surface of the olefin sheet of those partially torn away filaments. Also, there is typically significant stretching and wrinkling of the olefin material forming at least the flap portion and the portion of the package body receiving the flap portion in the region of the adhesive when such a package is opened. This causes a noticeable distortion of the package. Because the flap and body of an olefin sheet package are both typically damaged when the package is first opened, spunbonded olefin has not been used in multiple-use, sealed packaging.
It would be very desirable to incorporate spunbonded olefin sheet material into resealable, multiple-use package(s).